Sunan Ibn Majah 277
سنن ابن ماجه#277SahihIt was narrated that Thawban said:"The Messenger of Allah said: 'Adhere to righteousness even though you will not be able to do all acts of virtue. Know that the best of your deeds is Salat (prayer) and that no one maintains his ablution except a believer
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautHasan
Zubair Ali ZaiHasan
In-book reference: 1:11